HIBBING – One of the most impressive collections of core samples anywhere in the country can be found in three unassuming buildings in Hibbing.
The Drill Core Library run by the Minnesota Department of Natural Resources Lands and Mineral Division is home to more than 3.3 million linear feet of drill core — cylindrical selections of the ground beneath our feet unearthed using special drills from 9,000 holes around the state since the early 1970s.
According to DNR officials, it serves as the State of Minnesota's repository for archiving bedrock and earthen material core samples collected during minerals exploration, engineering, and geoscience research programs across the state.
The library attracts a world-wide audience of researchers, mineral explorers, and engineers who reuse existing core samples to develop new ideas about Minnesota's mineral resources and geology.
It’s sort of like the warehouse at the end of Raiders of the Lost Ark — but for sections of the stuff underneath our lawns and not the Ark of the Covenant.
According to Don Elsenheimer, an Economic Geologist for the DNR, the State of Minnesota has been collecting drill core for land management purposes since even before the DNR’s predecessor, the Department of Conservation, was established in 1931.
The first core library buildings at the DNR Hibbing location were built in 1972. The 1980
exploratory boring law drove dramatic expansion of the core library’s holdings, and
prompted the construction of two additional warehouses.
“We’re once again approaching shelf capacity, so planning has begun for the construction of a fourth drill core library building within the next couple of years,” he said.
According to DNR officials, the Drill Core Library provides a more efficient way to examine what is under the surface and reduces the need to drill duplicate cores.
This reduces costs — not just for mineral exploration but also road and bridge construction and research.
It has been estimated that it can cost $100,000 dollars to obtain the total core from 1,000 feet of drilling.
The DCL in Hibbing is the only State of Minnesota location for archiving core samples taken around the state. There are also about 7,000 mineral exploration cores, 1,500 roadway and bridge foundation cores, and 500 cores collected during scientific, governmental and academic research investigations.
Currently, the three buildings on site have the capacity to store about 4 million lineal feet of lineal feet of core samples, most of which are contained in two-foot long boxes, five core segments per box, or 10 feet per box.
Core building 1 was built in 1972 and holds 400,000 feet of core. Core Building 2 was constructed in 1979 and is home to 600,000 feet of core. Building 3, built in 1989 holds 800,000 and was expanded in 1995 to fit another 800,000 feet and again in 2009 to house 1.3 million feet of core.
“The DNR Core Library provides public access to core from all over the state. Our archive includes core drilled by exploration companies and public institutions like the Minnesota Geological Survey and DNR. We also get the core drilled by MnDOT for their road construction projects,” Elsenhemier said and there are several DNR employees at the Hibbing Office whose job responsibilities, at least in part, support Core Library operations.
“Most of the heavy lifting in the Core Library is done by our hard-working mining aides,” he added.
Samples are continuously being added to the collection.
“State law requires anyone who drills an exploratory borehole in Minnesota to submit at least a one-quarter portion of that core to the DNR core library so core samples from around the state will continue to be added to the repository to improve our knowledge and understanding of the state’s geological foundations,” Elsenheimer said.
A few of the major discoveries attributed to core stored at the facility include:
• An investigation of Platinum Group Element occurrence in stored drill core led to recognition of significant platinum and palladium content in Duluth Complex deposits and those elements account for about 20 percent of the estimated economic value of the copper nickel deposits.
• An investigation of copper-nickel cores led to a discovery of a previously unknown iron chloride mineral, which was ultimately recognized by the international mineral community and given the formal name “Hibbingite.” Since then it has been found in Ontario nickel deposits; in iron meteorites; and in the scale of swimming-pool pipes where chlorine reacts with iron.
• Examination of drill core from central Minnesota by the Kennecott Exploration Company led to a discovery of high-grade nickel-copper mineralization near the town of Tamarack, located west of Cromwell.
• Reconnaissance coring of potential dimensional stone sites in northeastern Minnesota by the DNR led to the development of three major stone quarries so far including the Mesabi Black, Lake Superior Green and Echo Lake Pink granite produced by Cold Spring Granite Company. The green was used for the D-Day memorial in Bedford, Va.